Sewing tape

ABSTRACT

Sewing tape which can be adhered to fabric, stitched through without gumming the needle and thereafter easily removed from the fabric is made by coating certain polyolefin film backings with a pressure-sensitive adhesive having a loss shear modulus greater than 106 dynes/cm2. At 7% elongation in the crossweb direction, the film shows a tensile stress of 75-250 kg/cm2 and a tensile force of 200-2,000 grams/cm.

United States Patent Pedginslri et a1.

SEWING TAPE Inventors: James J Pedginski, West St. Paul;

William A. Peper, Maplewood Village, both of Minn.

Minnesota Mining and Manufacturing Company, St. Paul, Minn.

Filed: Sept. 7, 1972 Appl. No.: 286,992

Assignee:

US. Cl..... 117/68.5, 117/122 PF, 117/122 PA, 117/14, 117/45 llnt. C1. C09j 7/02 Field of Search 117/122 PF, 122 PA, 76 A, ll7/68.5

References Cited UNITED STATES PATENTS 4/1959 Ulrich 117/122 8/1964 Schaffhausen 1. 117/122 X Dec. 19, 1974 3,396,837 8/1968 Schmelzle et a1 ll7/122 X 3,406,039 10/1968 Paufler.... 117/122 X 3,462,284 8/1969 Vertnik 117/122 3,661,618 5/1972 Brookman et a1. 117/122 X 3,733,292 5/1973 Sirota et a1. 1 17/122 X Primary Examiner-William D. Martin Assistant Examiner Bernard D. Pianalto Attorney, Agent, or Firm-Alexander, Sell, Steldt & DeLaHunt 5 7 ABSTRACT 3 Claims, No Drawings SEWING TAPE BACKGROUND OF THE INVENTION This invention relates to normally tacky and pressure-sensitive adhesive tape, and particularly to tapes having utility in sewing, dressmaking, tailoring, and similar procedures.

For at least a decade normally tacky and pressuresensitive adhesive tape has been employed in sewing operations. For example, transparent tape is used to tape a pattern to fabric, the seamstress or tailor thereafter cutting through both the tape and the pattern. Tape can be adhered to fabric to provide a straight edge along which a seam is to be sewed; it has also been employed to hold pockets, decorative lace, rickrack, braid, applique, and other trimming in place on an underlying fabric to which they are to be sewn, thereby eliminating a time-consuming basting step. There are other situations where transparent tape has sometimes been applied to two plies of fabric, a seam stitched through both tape and fabric, and the tape then removed. Many pressure-sensitive adhesives gum a rapidly moving sewing machine needle, and this procedure has thus not been recommended. Further, previously available tape which had been stitched to an underlying fabric tended to tear and sliver and was removed only with great difficulty. Top stitching operations, where two or more closely spaced stitch lines were applied, aggravated the tape removal problem, and a zig zag or other decorative stitch made tape removal intolerably tedious and annoying. Attempts to remove other tapes sometimes require a force so great that the stitches are actually loosened and lifted, e.g., in sewing muslin with mercerized cotton thread.

SUMMARY OF THE INVENTION The present invention provides a normally tacky and pressure-sensitive adhesive tape which not only has unique construction but which also possesses unique and valuable characteristics for use in sewing operations. Like previous tape products, the tape of the present invention can be used to assist in the spacing and alignment of button holes, the temporary positioning of zippers, pockets or decorative trim, etc. Unlike previous products, however, the present tape product can be stitched through with a high speed sewing machine without gumming the needle, and even in the case of top stitching or zigzag stitching, the tape can thereafter be removed easily and simply.

The tape of the invention comprises a self-supporting film backing consisting essentially of polyolefin having specific physical properties, with a layer of normally tacky and pressure-sensitive adhesive applied to one face of the film and likewise possessing certain specific physical properties. The film, at an elongation of 7% in the cross direction, displays a tensile stress of about 75-250 kglcm and a tensile force of about 200-2,000 gms/cm, the thickness to achieve this tensile force being in the range of about 25-250 microns, and preferably 40-80 microns. The adhesive layer is at least about 12 microns (preferably 15-25 microns) thick and has a loss modulus as hereinafter defined of more than 10 dyneslcm At this point it should be noted that pressuresensitive adhesive tapes having polyolefin film backings and designed for packaging and wrapping purposes are broadly old in the art; see, e.g., U.S. Pats. Nos.

2,631,954, 3,079,278, 3,088,848, 3,241,662, 3,265,769 and 3,372,049. The strength and high modulus characteristics sought in such backings, however, do not provide a product suitable for use as a sewing tape. Similarly, the physical characteristics which have been empirically found essential for a satisfactory sewing tape are not desired for conventional tapes.

DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS In order to improve understanding of the invention, it is believed that it will be helpful to describe certain tests which are used in measuring either components of the sewing tape or the performance of the finished tape itself.

Tensile Force A strip offilm 2.54 cm (1 inch) wide and 20.3 cm (8 inches) long is cut in the cross web direction of a backing which is to be tested. Opposite ends of the film are then clamped in the jaws of a tensile testing machine having a chart which records force vs. elongation, the jaws initially being 12.7 cm (5 inches) apart. The jaws are then separated at the rate of 12.7 cm/minute until they are at least about 14.0 cm apart; the tensile force at 7% elongation is then read from the chart. This force, in grams, is divided by 2.54 to obtain the tensile force expressed in terms of gms/cm width; the resultant figure should be in the range of about 200-2,000 gms/cm for the film to be useful as a backing for sewing tape. If the tensile force falls below 200 gms/cm, the tape can not be removed cleanly, leaving fragments below the stitches. On the other hand, if this force exceeds 2,000 gms/cm, stitch loosening often results on removal of the tape.

- Tensile Stress The tensile force in gms/cm, determined as described in the preceding paragraph, is divided by the film thickness in centimeters and the value further divided by l,000 (gms per kilogram) to obtain a value expressed in kg/cm The resultant tensile stress should be in the range of about -250 kg/cm If the tensile stress value falls below the range, the tape tends to tear randomly during removal, while if the upper end of the range is exceeded, the tape is excessively brittle, typically slivering" during removal.

It will be readily apparent that the tensile stress is substantially independent of thickness but that the thickness of a film can be increased or decreased to obtain an appropriate tensile force. The film thickness itself should, however, fall within the range of about 25-250 microns, preferably 40-80 microns. If the thickness falls much below 25 microns, the tape unfortunately conforms and adheres so well to fabric that it is extremely hard to remove after stitching. On the other hand, if the thickness exceeds 250 microns, there is a tendency for stitches to loosen when the-tape is removed, even where double-knit polyester fabric is stitched with a stretch thread. Adhesive loss shear modulus An adhesive film about 300 microns thick is prepared by spin casting a solution thereof in a polytetrafluoroethylene-lined cup, partially drying the film, removing it, and drying it 30-40 hours in a vacuum oven maintained at 40C. Pieces of film about 1.0 X 0.35 cm are then die cut from the film and tested in a shear rheometer. The piece of adhesive film to be tested is placed on the piezoelectric sensor plate of the rheometer, where its dimensions are accurately measured, after which it is clamped firmly between the sensor plate and electromechanical driver plate, static compression of the film sample being about l-l5%. The driver plate is then actuated by a power oscillator at 23C. and a frequency of 20 Hz*, the piezoelectric sensor generating voltages which are read by a vector voltmeter and converted to shear storage modulus (G') and shear loss modulus (0") values. It has been empirically determined that an adhesive whose shear loss modulus exceeds dynes/cm at Hz and 23 C. will not gum a sewing machine needle, while one whose shear loss modulus falls significantly below that figure tends to do so. The upper limit of loss shear modulus need not be numerically established, since an excessively firm adhesive will not be pressure-sensitive, i.e., possess the long-recognized 4-fold balance of adhesion, cohesion, stretchiness, and elasticity; see U.S. Pat. No. 2,750,315, Col. 6, lines 40 et seq.

Tape removal *lf the electronic accessories used with the shear rheometer are incapable of providing accurate modulus data at frequencies as low as 20 Hz, one plot ofG" vs frequency may be made at 23C. and another at 41C., the two plots then being superimposed to obtain an extrapolated value at a lower frequency; see, c.g., the procedure described in Ferry. Viscoelastic Properties of Polymers, John Wiley & Sons, Inc., i970, pp. 292-351 and Tobolsky, Properties and Structure of Polymers", John Wiley & Sons, Inc., 1960, pp. l44l52.

In evaluating the performance of sewing tapes, the following procedure is used: A double-knit creped polyester material (3 square yards/lb.) is folded so that a double layer about 6 inches square results. Three pieces of test tape inch wide X 4 inches long are then laid across the material parallel to the machine direction of the fabric. A 4% pound rubber roller is then passed over the tape and the material, which is supported on a flat table, four times to insure close contact and adhesion between the tape and cloth. Using an electric sewing machine capable of zigzag sewing (e.g., a Singer Touch & Sew Model No. 758) with normal presser foot pressure, thread tension set at 9, No. 14 ball point needle, spun polyester extra strong thread, a stitch setting of l2/inch, a width setting of zero, and a slow speed setting (ll cycles/second), a single straight line is sewed through the center of one of the tape samples from end to end, using the maximum rate available at a slow speed setting.

Using the equipmentjust described, the stitch setting is changed to 8/inch and 3 parallel lines of stitches onefourth inch apart are sewed down the length of the second strip of tape, thereby simulating a common method of top stitching.

Using the procedure described in connection with straight stitch sewing, the width is changed to the No.

i 3 position (l/l6-inch width) and a zigzag stitch sewed down the entire length of the third strip of tape.

Test samples are allowed to remain at room temperature for 18 hours, after which each of the three tapes is removed, using a jerky tearing motion, about one inch of tape at a time. The person performing the test removes the tape from only one side of a line of stitching at a time, pulling the tape up at a 45 angle to the fabric and across the stitches at a 45 angle to the edge of the tape. Each test is scored separately and a composite total computed. One point is scored for each stitch under which a residue of tape remains, and one point for each time the tape tears so that the removal strip has to be restarted. The maximum points for an acceptable product are as follows: straight stitch, 2; top stitch, l5; zigzag stitch, 15; total, 29. Needle gumming A solution of pressure-sensitive adhesive is coated on a silicone-treated release liner and the solvent evaporated to leave a dry thickness of about l8-2O microns (0.7-0.8 mil). A 4-inch X 10-inch piece of mercerized cotton rib woven flannel having a soft brushed finish, about 5 square yards/lb. is adhered to the exposed face of the adhesive. A No. 14 needle is washed in methylethyl ketone, air dried, placed in a sewing machine and threaded with No. 50 white mercerized cotton thread. The machine speed is set at slow, the stitch width at zero, and the stitch setting at 12/inch. An 8-inch length is then stitched through the cloth:adhesive:liner laminate (cloth side up) at the maximum slow speed setting (11 cycles/second). The needle is then removed from the machine and a 7X magnifying glass used to determine whether any residue remains. The test is repeated at fast speed (l8 cycles/second). The stitch setting is then increased to 20/inch and the test again run at both slow and fast speeds. There should be no adhesive visible on the needle.

The invention will now be described with respect to specific illustrative but nonlimiting examples, in which all parts are by weight unless otherwise noted.

EXAMPLE 1 Forty parts of medium density (0.935) polyethylene (commercially available from Gulf Oil Company under the designation Gulf 2604M" was blended with one part of yellow polyethylene resin concentrate (commercially available from Eastman Chemical Products, Inc. under the trade designation l830E-77225) and extruded as a 3.5-mil (89-micron) film. After extrusion at 450F. the polyethylene film was quenched slowly on internally water-cooled rolls maintained at 180F., causing it to have a relatively high degree of crystallinity. The film was then conventionally corona treated on both sides, using two electrodes, 18 amps/electrode, at 50 feet per'minute; after which a black nitro-cellulose ink was flexographically printed on one side in the form of dashed lines one-fourth inch apart, extending in the machine direction of the film; at /2-inch intervals along each dashed line a cross was printed, the crosses on adjacent dashed lines being staggered, one-fourth inch. A 14% toluene solution ofa :10 iso-octyl acrylatezacrylic acid copolymer pressure-sensitive adhesive was then coated on a silicone-coated kraft paper release liner and the solvent evaporated to leave a dry adhesive weight of 3.6-4.0 grams per 24 square inches, corresponding to a thickness of about 18 microns (0.7 mil). This adhesive was then transferred to the unprinted side of the previously prepared yellow polyethylene film, after which the printed side was provided with a polyvinyl carbamate low adhesion backsize as described in Dahlquist et al US. Pat. No. 2,532,01 l. The tape was then slit to 36-inch width in such a manner that three machine direction lines appeared and wound convolutely about a core in the form of 25-foot rolls.

The tape described in the preceding paragraph of this Example adhered well to a variety of fabrics, could be stitched through without gumming the sewing machine needle, and was thereafter readily removable without undue tearing or slivering.

For convenience in analysis, there are now provided @163 -fi 'q acrylalelmflhyl esrylflwiasrylw actdzglycldyl methacrylate copolymer. commercially a Senes of tabulated examplesi mcludmg Certam unsat' available from Monsanto Chemical Co. as (iclva 263" TABLE 1* At 7% cross- Acceptable Backing film web elonwtion Tape removal rating points (A) or an Tensile Tensile acceptable Thickness. stress, force. (U) remov- Example Composition microns kg/cm gms/cm Straight Top ZigZag Total ability Lim 25-250 75-250 200-2000 2 l5 15 29 l MDPE 89 1 17 1040 3 8 A 2 do. 63 100 630 0 10 A 3 LDPE 68 74 500 0 18 10 28 Borderline 4 do. 62 53 329 10 34 31 75 U 5 HDPE 41 172 705 0 9 2 l 1 A 6 do. 79 191 1510 0 5 5 10 A 7 lPP (4.0) 86 281 2420 0 15 28 43 U 8 11? (0.8) 81 182 1470 0 0 13 13 A 9 Cellulose 51 496 2530 23 8 61 U acetate 10 Biaxially 28 1010 2830 4 12 43 59 U oriented polyethylene terephthalate ll Cellophane 34 580 1970 4 25 24 53 U Pressure-sensitive adhesive same as in Example 1. so gumming is not a problem.

TABLE 11* Adhesive Adhesive loss shear Acceptable (A) or Thickness. modulus (6"). dynes/ unacceptable (U) Example Type microns cm X 10 at 20 Hz needle gumming Limits i 12 1 l 10A:AA (90:10) 16 7.93 A 12 lOA:AA (97:3) 18 0.45 U 13 AR-1107 18 0.26 U 14 0263 16 3.99 A

" Film backing same as in Example 1. so tape removal not a problem.

isfactory tape products, to help in delineating'the invention. (1n the interest of completeness, Example 1 is repeated in each table.) The following abbreviations are employed:

LDPE

MDPE

lPP

lOA

AA lOAzAA iso-TBS iso-BT hex oct PVEE PViBE AR-l 107 PVnBE NSR AR-l044 low density (0.917) polyethylene, melt flow index 0.75 gm/10 min.. commercially available from Union Carbide as DFD-5505.

medium density (0.934) polyethylene. melt flow index 1.2 gms/IO min.. commercially available from Sinclair Koppers as Super Dylan 6560" isotactic polypropylene. 0903-0904 density. melt flow index in gms/l0 min. shown in parentheses. commercially available from Hercules Chemical Company as Profax iso-octyl acrylate. i.e.. acrylic acid ester of the mixed isomers of octyl alcohol acrylic acid copolymer of monomers. weight ratio shown in parentheses; inherent viscosity (ethyl acetate). 1.5-2.1 rubber-resin pressure-sensitive adhesive in which 100 parts of polyisoprene is tackified byblending there with 75 parts of poly-tcrt-butyl styrene. the molecular weight of the tackifier being shown in parentheses polyisobutylene. commercially available from BASE as Oppanol 8-150" polyhexene. having an inherent viscosity (toluene) 5.4 polyoctene. inherent viscosity (toluene). 3.2-4.0 polyvinyl ethyl ether. commercially available from Union Carbide as EDBM polyvinyl iso-butyl ether. commercially available from BASF as Oppanol C/KV-125 homopolymer of n-butyl acrylate. commercially available from Ashland Chemical Company polyvinyl n-hutyl ether. inherent viscosity (benzene). 3.3 2-cthylhexyl acrylatezethyl acrylatezvinyl acetatezacrylamide copolymer. commercially available from National Starch Company as Resyn 78-3240" 2-ethylhexyl acrylatezvinyl acetatezacrylic acid: ethylacrylate copolymer. commercially available from Ashland Chemical Company Z-ethylhexyl acrylatczvinyl acetate copolynier. commercially available from Monsanto Chemical Co. as Gelva 260" The following table shows the relationship between an adhesives loss shear modulus and its tendency to gum a sewing machine needle, using the tests previously described:

TABLE 111 Adhesive Loss Acceptable shear modulus (A) or (6") dyneslcm unacceptable Example Adhesive 10" at 20 Hz (U) needle gumming Limit 1 l5 -o-TBS(1600) 0.16 U 16 oct 0.17 U 13 AR-l 107 0.26 U 17 PVEE 0.32 U 12 lOA:AA (97:3) 0.45 U 18 PVnBE 0.63 U 19 hex 0.81 U 20 IOAIAA (9515) 1.04 A 21 iso BT 1.24 A 22 1OA1AA (9317) 2.15 A 23 NSR 2.34 A 24 AR-1044 2.64 A 14 G 263 3.99 A 25 PViBE 5.09 A 1 IOAzAA (:10) 7.93 A 26 G 260 11.1 A 27 iso-TBS (10.000) 15.1 A

Except for coloring material, each useful backing film described above consists essentially of a homopolymer of polyethylene or polypropylene. Copolymers of more than one olefin monomer. including higher monomers. may also be employed. provided that the ultimate film possesses the previously specified physical properties. In like manner, blends of separately prepared polyolefins may be incorporated into the film backing. Minor amounts of other monomers may be copolymerized with one or more olefin monomers in the same way, just as minor amounts of other polymers may be blended with polyolefin. Those skilled in the art will also appreciate that minor amounts of pigments, processing aids, fillers and the like may be included in the backing.

What is claimed is as follows:

1. A colored, matte-finished normally tacky and pressure-sensitive adhesive tape provided with repeating printed indicia at predetermined intervals and having particular utility in sewing procedures, comprising in combination:

a. a self-supporting medium to high density polyethylene film backing, having, at 7% elongation in the cross direction,

1. a tensile stress in the range of about 75 to 250 kg/cm and 2. a thickness in the range of about 40 to microns, such that the tensile force is in the range of about 400-2,000 gms/cm width;

b. coated on one surface of said backing a layer of normally tacky and pressure-sensitive adhesive which 1. is in the range of about 12 to 15 microns thick and 2. has a loss shear modulus of more than 10 dynes/cm whereby the tape can be adhered firmly to fabric, stitched through rapidly using an electric sewing machine without gumming the needle, and completely and easily removed from a line of stitching which extends therethrough without loosening the stitches.

2. The tape of claim 1 wherein the adhesive is a :10

iso-octyl acrylatezacrylic acid copolymer.

3. The tape of claim 2 wherein the film is a medium density polyethylene. 

1. IS IN THE RANGE OF ABOUT 12 TO 15 MICRONS THICK AND
 1. A TENSILE STRESS IN THE RANGE OF ABOUT 75 TO 250 KG/CM2 AND
 1. A COLORED, MATTE-FINISHED NORMALLY TACKY AND PRESSURESENSITIVE ADHESIVE TAPE PROVIDED WITH REPEATING PRINTED INDICIAAT PREDETERMINED INTERVALS AND HAVING PARTICULAR UTILITY IN SEWING PROCEDURES, COMPRISING IN COMBINATION: A. SELF-SUPPORTING MEDIUM TO HIGH DENSITY POLYETHYLENE FILM BACKING, HAVING, AT 7% ELONGATION IN THE CROSS DIRECTION,
 2. A THICKNESS IN THE RANGE OF ABOUT 40 TO 80 MICRONS, SUCH THAT THE TENSILE FORCE IS IN THE RANGE OF ABOUT 400-2,000 GMS/CM WIDTH; B. COATED ON ONE SURFACE OF SAID BACKING A LAYER OF NORMALLY TACKY AND PRESSURE-SENSITIVE ADHESIVE WHICH
 2. The tape of claim 1 wherein the adhesive is a 90:10 iso-octyl acrylate:acrylic acid copolymer.
 2. has a loss shear modulus of more than 106 dynes/cm2, whereby the tape can be adhered firmly to fabric, stitched through rapidly using an electric sewing machine without gumming the needle, and completely and easily removed from a line of stitching which extends therethrough without loosening the stitches.
 2. a thickness in the range of about 40 to 80 microns, such that the tensile force is in the range of about 400-2,000 gms/cm width; b. coated on one surface of said backing a layer of normally tacky and pressure-sensitive adhesive which
 2. HAS A LOSS SHEAR MODULUS OF MORE THAN 10**6 DYNES/CM2, WHEREBY THE TAPE CAN BE ADHERED FIRMLY TO FABRIC, STITCHED THROUGH RAPIDLY USING AN ELECTRIC SEWING MACHINE WITHOUT GUMMING THE NEEDLE, AND COMPLETELY AND EASILY REMOVED FROM A LINE OF STITCHING WHICH EXTENDS THERETHROUGH WITHOUT LOOSENING THE STITCHES.
 3. The tape of claim 2 wherein the film is a medium density polyethylene. 